Closure Scheme Optimization Of Rigid Frame Continuous Composite Bridge And Block 0 Study On Temperature Effect Of Hydration Heat

With the rapid development of transportation,rigid frame continuous composite bridge is widely used in bridge construction.Rigid frame continuous composite bridge has a large number of spans,and there are many closure sequences.Selecting the appropriate closure sequence can optimize the mechanical properties of the bridge in the construction stage and service stage.Several piers in the middle of this type of bridge are consolidated by pier beams.Before closure,jacking is required to offset the excessive deviation of the consolidated pier due to closure sequence,closure temperature difference,concrete shrinkage and creep.Selecting the appropriate jacking position and thrust can bring convenience to the construction and optimize the mechanical properties of the bridge.This type of bridge is constructed by cantilever construction method,which has high requirements for Block 0.Block 0 has complex structure and thick components,which can be regarded as mass concrete.No.0 block usually uses high-strength concrete with high cement content and large temperature effect of hydration heat.When the internal and external temperature difference is too large due to improper construction or maintenance,it is very easy to produce temperature cracks.Therefore,the hydration heat effect of No.0 block can not be ignored.It is necessary to analyze the hydration heat effect of No.0 block and take corresponding optimization schemes to prevent the occurrence of temperature cracks in No.0 block.Taking a rigid frame continuous composite bridge as an engineering case,this paper analyzes the closure sequence,pushing and hydration heat effect of Block 0 of the bridge,so as to provide theoretical research for making the bridge reach the optimal state after completion and avoiding the occurrence of temperature cracks in Block 0.The main research results and contents of this paper are as follows:(1)Collecting and consulting the literature on closure and jacking of rigid frame continuous composite bridge and the hydration heat of concrete in Block 0,this paper analyzes the key points of closure and jacking,and expounds the basic theory and calculation method of hydration heat of concrete.(2)Using Midas civil finite element analysis software,the finite element analysis model of the whole construction process of rigid frame continuous composite bridge is established.The stress and deformation of the main beam under four different closure schemes are compared and analyzed,and the better two schemes are selected.On this basis,the best closure scheme is determined considering the role of jacking.The local model of the jacking position of the box girder is established,and the local stress and deformation of the box girder under the action of the jacking force of the best closure scheme are studied.(3)The finite element simulation analysis of the pouring process of Block 0 is carried out by Midas FEA,the variation law of hydration heat temperature field of Block 0 is revealed,the temperature and stress of some positions of the top plate,flange,web and bottom plate are analyzed.It is concluded that the maximum hydration heat temperature appears at the diaphragm and the temperature stress at some positions exceeds the limit.(4)This paper analyzes the feasibility of reducing the hydration heat temperature of Block 0 from the types of cement,molding temperature,layered pouring and cold pipe arrangement,and analyzes the common treatment measures after the occurrence of temperature cracks.